In 753 the pope, Stephen II, makes an unusual journey north of the Alps. He visits the Frankish king, Pepin III, to seek his help against the Lombards who have recently taken the city of Ravenna and who now pose a similar threat to Rome. The pope anoints Pepin at the abbey of St Denis, near Paris, together with his two young sons Charles and Carloman. Pepin duly invades northern Italy in 754, and again in 756.

He is able to drive the Lombards from the territory belonging to Ravenna. But he does not restore it to its rightful owner, the Byzantine emperor. Instead, perhaps believing the fiction revealed in the forged Donation of Constantine, he hands over large areas of central Italy to the pope and his successors.

The land given to pope Stephen in 756, in the so-called Donation of Pepin, gives the papacy the added role of a temporal power. These lands, increased and reduced at various periods of history, are the papal states over which the popes continue to rule until their incorporation in the new kingdom of Italy in 1870.

In the short term the temporal rule of the popes is shaky. Within a few years the Lombards again invade their territory. In 772 a new pope appeals for help to a new Frankish king. Adrian I enlists the support of Charlemagne. This time the Lombard threat is conclusively resolved. But northern Italy, now within the Frankish empire, is reduced to an appendix of France and Germany.

Fragmented Italy: from the 7th century

Viewed on the map, Italy, with Sicily at its toe, looks the most natural of political units. Protected from mainland Europe by the Alps, and on all other sides by the sea, this surely must be a single kingdom - or, as the Romans made it, the secure centre of an empire.

Yet its geographical position has had precisely the opposite effect. To either side of the Alps there is space through which armies from western or eastern Europe can force their way into the rich green territory of the Po valley. And the fertile coasts of Italy and Sicily are all so close to other stretches of land that a short sea crossing seems more of an invitation than a deterrent to neighbouring rivals.

The entire eastern coast is vulnerable to attack from the Balkans. Sicily is a short hop from Africa. Corsica and Sardinia provide useful stepping stones for enemies based in southern France or Spain.

All these links can also work to the advantage of the inhabitants of Italy, as the Genoa and Venice triumphantly prove. But they mean that Italy does not have the inward strength of an island. It has, instead, the outgoing opportunities - and with them the vulnerability - of a rich peninsula crowded in upon by interested rivals. After the collapse of the Roman empire Italy is constantly nibbled at by its neigbours, making the map an ever-shifting quilt. There is only one fairly stable element - the papacy in Rome.

Nibbling neighbours: 9th - 13th century

In the 9th century the Byzantine emperor still holds various territories down the east coast (the exarchate of Ravenna) together with Sicily. The pope in Rome rules over the papal states. Northern Italy is now officially part of the empire of the Franks, invited into the peninsula by Rome to suppress the Lombards.

Over the coming centuries much of Italy is often in the hands of small local princes, but there are also frequent intruders. In the early 10th century, Hungarians regularly raid into northern Italy. Arabs from north Africa have by that time captured Sicily from the Byzantines, together with maritime towns on the Italian mainland. In 846 they besiege and partly sack Rome.

The anarchy which prevails for much of the period in the north of Italy has a profound effect on the region. It causes the more important towns, now growing in prosperity, to enclose themselves in strong walls and to adopt an increasingly independent stance. The government of these towns is taken into the hands of the leading citizens, resulting in the extremely effective Italian oligarchies usually referred to as communes - such as Venice, Milan, Genoa, Pisa, Florence, Siena and many others.

In south Italy and Sicily a different pattern develops, because this southern area is dominated by a succession of powerful dynasties from overseas.

The island of Sicily, in particular, suggests the degree of foreign involvement in this region during the medieval centuries.

The Arabs take Sicily from the Byzantines by a slow process of attrition between 827 and 965. The Normans conquer it between 1060 and 1091. In 1194 it comes by marriage into the possession of the German Hohenstaufen dynasty. Papal intrigue grants the island in 1265 to the Anjou branch of the French royal family. Finally Sicilian hostility to the French, violently expressed in the Sicilian Vespers of 1282, results in the involvement of the ruling family of Aragon, beginning a long connection with Spain. For much of this time the island is linked with southern Italy, as the kingdom of Naples.

Communes in Italy: 11th - 13th century

The period from the 11th to the 13th century sees a steady rise in prosperity in the cities of Europe. One of the first regions to prosper is northern Italy - on the trade route between the eastern Mediterranean and northern Europe, with goods landing at Venice for the journey through the passes of the Alps, north to Austria and Germany or west through Milan to France.

Yet northern Italy is politically insecure, crushed between the rival claims of imperial Germany to the north and the papal states to the south. Prosperous but threatened, the cities seek greater control of their own destiny. The result is the form of government known to historians as the medieval commune.

Between about 1080 and 1140 many of the towns of northern Italy (among them Pisa, Siena, Florence, Bologna, Milan and Genoa) acquire municipal councils in which the elected councillors call themselves consuls - in a deliberate echo of Italy's republican past.

As these republican communes grow in wealth, and assert control over large tracts of the surrounding countryside, they become in effect independent. Technically they acknowledge either pope or emperor as feudal overlord. Unable to restrain these fledgling city states, popes and emperors often authorize their new form of government and thus give it legitimacy.

In the early years of these Italian communes every male citizen can participate in an assembly known as the arengo. But this glimmer of democracy is soon extinguished in favour of oligarchy. Considerations of efficiency coincide with the interests of the nobility and the rich merchants of the city. Electoral power in the communes becomes increasingly restricted to members of a few families.

This process in its turn leads towards authority in each city being placed in the hands of one man. The noble families constantly feud within the communes, just as the communes regularly go to war against each other. The practical solution is a powerful chief executive.

During the last three decades of the 12th century nearly all the north Italian communes appoint a mayor or podestà (someone with potestà, 'power') to run the city's affairs. The podestà is usually a nobleman from another district, who arrives with his own household and administrative staff. His appointment is for a fixed term, rarely more than a year.

But once the machinery of individual rule is in place, a more permanent and even perhaps hereditary ruler becomes a likely option. During the second half of the 13th century the podestá gives way to the signore.

In commune after commune, from the late 13th century, the local oligarchs accept a powerful leader as their signore and subsequently allow the post to remain with a family. The Visconti of Milan are an early example. Matteo Visconti is signore from 1287 to 1322 and the post is declared hereditary in 1349. Florence remains technically a republican commune for very much longer; the Medici only become hereditary dukes in 1532.

In this way the near-democracy of the early Italian communes reverts gradually to princely rule. The one exception is the earliest commune of them all. The self-perpetuating oligarchy of Venice is a refined system which preserves power in the hands of the local grandees until the 18th century.

Venice, Genoa and Pisa: 9th - 14th century

The first of Italy's medieval cities to prosper are those which grow rich through maritime trade - Venice in the east, Genoa and Pisa in the west. Venice, with the Byzantine empire as its neighbour on the other side of the Adriatic, upholds its own interests from as early as the 9th century through skilful diplomacy.

Genoa and Pisa, by contrast, are strengthened through conflict. In about 934 Genoa is sacked by a Fatimid fleet from north Africa. Muslim raids of this kind are a regular hazard in Corsica and Sardinia, the two large islands confronting the west coast of Italy.

The Italian communes of the west coast demonstrate their strength in the 11th century when Genoan and Pisan fleets, often working in alliance, protect Corsica and Sardinia from the depredations of Muslims. Both cities subsequently develop extensive trade in the western Mediterranean. Genoa also plays a large part in the crusades, establishing strong trading links in the eastern Mediterranean and coming into direct competition with Venice.

Warfare between these two Italian city states is long and intermittent, with Venice by no means always the stronger - until the issue is finally resolved in 1380 at Chioggia.

Republican Florence: 12th - 16th century

When Florence begins its territorial expansion, in the 12th century, the town - like many others in northern Italy - is governed as a commune. The Florentines resist princely rule longer than any other commune apart from Venice, not finally succumbing until the Medici are accepted as dukes of Tuscany in the 16th century.

During the four centuries of the republic, Florence is in permanent turmoil as rival classes jockey for power. The city's astonishing achievement, not untypical in Italian history, is that amid the murder and the mayhem Florence grows prosperous and produces outstanding masterpieces of literature and art. Indeed this troubled city becomes the powerhouse of the Renaissance.

Florence's internal feuds are even more complex than those of other Italian cities. There is the usual clash between the nobles and the rich merchants and craftsmen of the city guilds. This struggle seems to be won by the merchants in 1282, when they pass a law restricting civic office to members of the guilds.

But the nobles continue to wield great power by other means (and even return to office by the subterfuge of becoming guild members themselves).

Meanwhile there is a similar struggle between the richer guilds and the lesser guilds, sometimes with the added complication of pressure from workers who are not allowed to join a guild. In 1378 there is an uprising by the Ciompi, who work for day wages in Florence's main industry, the manufacture of cloth.

On this occasion the labourers so frighten their employers that for a few weeks they are represented in the city's government - a brief experiment in something approaching democracy, until the new laws are revoked and Florence reverts to the commune's more normal oligarchy.

Factions within the ruling classes are aligned in Florence, as elsewhere in medieval Italy, in terms of support for the papal or imperial parties - Guelphs versus Ghibellines. Florence inclines mainly to the papal cause (putting it at regular risk from marauding imperial armies), but even this apparent unanimity does not prevent violent factionalism. The Guelphs of Florence divide into bitterly opposed groups, the Blacks (more energetic in their support of the pope) versus the Whites.

Individual lives are disrupted or cut short by these rivalries (as when Dante is exiled from Florence in 1301) but the city continues to prosper. It does so partly on wool. But Florence is also a city of bankers.

Italian condottieri and Swiss guards: 13th - 16th c.

From the late 13th century the citizens of the Italian city states prefer to employ mercenary armies to fight their battles rather than go to war themselves. The need is supplied by powerful lords, known as condottieri (meaning under 'contract'). They provide more than their own services as generals. They bring with them large professional armies.

In the 14th century these armies, or companies, are largely foreign. One of the first, known as the Great Company, numbers some 7000 heavily armed cavalry and 1500 infantry. These men are led first by a German knight, Werner von Urslingen, and then by a Frenchman, Montreal d'Albarno.

With excellent internal discipline and complete disregard for the interests of anyone else, such armies become the terror of Italy. Montreal's achievement on behalf of the Great Company in 1353 demonstrates the scale of the organized brigandage. During that year he extracts 16,000 florins from Pisa, 16,000 from Siena, 25,000 from Florence and 50,000 from Rimini.

In the following year Montreal becomes over-confident. When his company is involved in a war against Milan, he goes on his own to Rome to collect some debts from Cola di Rienzo. Rienzo's way of paying the debt is to behead Montreal as a brigand.

Later in the 14th century the most famous army in Italy is the White Company of John Hawkwood, who brings a party of adventurers south during a lull in the Hundred Years War. More responsible than his predecessors, Hawkwood becomes a faithful servant of Florence - serving as the city's captain general from 1378 to 1392 and being honoured posthumously with a fresco of himself on horseback in the cathedral.

Hawkwood is the last of the great foreign condottieri. In the 15th century Italian nobles, often with their own estates to maintain, hire out their services and those of their retainers as private armies.

Many of these Italian condottieri of the 15th century are extremely civilized men of the Renaissance (Federico da Montefeltro, with his own court at Urbino, is an outstanding example). Engagements between their armies and others like themselves are often elaborate rituals, in which little harm is done except to the pockets of their employers.

By the end of the century the role of the condottieri is considerably reduced. Warfare on Italian soil is now on an international scale. And there has been a change in the art of war. The condottieri are mounted knights, relics of a medieval past. Battles now are won by infantry and guns.

Venice and the Veneto: 14th - 15th century

While the Venetians are acquiring islands on the route to the Middle East, they also gain control of a large part of the Italian mainland. The first territory to be won is the region adjacent to their own lagoon - the Veneto (named like Venice itself from an Indo-European tribe, the Veneti, who migrated here in about 1000 BC).

Venice occupies these mainland territories by force. But the Venetian role is that of the jackal coming in after the lion.

The lion in northern Italy in the late 14th century is Gian Galeazzo Visconti, the signore of Milan. Gian Galeazzo is a voracious conqueror, suspected in his own time of harbouring the ambition to become king of all Italy. He systematically seizes the territories of lesser signori. Those lying between Milan and Venice include Verona and Vicenza, two cities ruled by the della Scala family (known also as Scaliger in the Latin version of their name).

Vicenza falls to Gian Galeazzo in 1384 and Verona in 1387. His next target is Padua, ruled by the Carrara family, which he takes in 1388.

Padua is recovered for the Carrara in 1390 with Venetian help, but its long-term independence looks unlikely as Gian Galeazzo's realm continues to expand. Pisa and Siena accept his rule in 1399; he captures Bologna in 1402; but later that year, as he is preparing to attack Florence, he dies suddenly of the plague.

The rapidly enlarged Visconti realm crumbles on Gian Galeazzo's death, and Venice is on hand to pick up some of the pieces. Vicenza is captured in 1404, followed by Verona and Padua in 1405. A generation later, with the Veneto now securely Venetian, the republic's territory is further enlarged to north and west.